In general, gas turbine combustion systems adopt a premixing combustion scheme for NOx reduction in many cases. These gas turbine combustion systems have a structure in which one diffusion combustion pilot nozzle at the center and a plurality of premixing nozzles (main nozzles) for performing premixing combustion around the diffusion combustion pilot nozzle are arranged.
In the gas turbine combustion systems based on the premixing combustion scheme, there is a possibility of occurrence of a flashback phenomenon (flashback) in which a flame goes back into a pre-mixer because a fuel temperature enters a combustible region. Accordingly, a design for preventing the flashback phenomenon or a design for enabling immediate restoration by detecting the flashback phenomenon is required to maintain safe operation of a gas turbine combustion system.
For example, a combustion system in which a flashback analysis device analyzes whether flame backflow (a flashback) occurs is disclosed (see Japanese Unexamined Patent Application, First Publication No. Hei 8-68537). The combustion system stops pre-mixing combustion of a main fuel when an analysis result indicates the occurrence of flame backflow and injects the main fuel as a changeover fuel from a pilot fuel nozzle.